1. Field of the Invention
The invention relates to determining the existence of alignment defects in shafts that are disposed one behind the other.
2. Description of Related Art
A first known method is the so-called prism method. In the case of this method, the emitter for emitting the alignment measurement beam and the associated electrooptical position detector are situated on one and the same shaft, and the alignment measurement beam is directed at a rectangular reflecting prism, which faces it by its hypotenuse plane and which is rigidly mounted on the other shaft and reflects the light beam to the position detector with an angle of reflection which is dependent upon the respective state of alignment, so that the position of the point of incidence of the light beam on the light-sensitive detector surface is likewise dependent upon the state of alignment.
Another known method is the so-called dual radial method, in the case of which two light emitters and two biaxial electrooptical position detectors are used; in this case, a position detector and a light emitter are disposed on each shaft and the light emitter on one of the shafts sends the alignment measurement beam to the position detector on the other shaft.
There are various known modes of implementation of the abovementioned methods, e.g. one in which the mutually coupled shafts are rotated in each case through 90.degree. and measurements are made in at least three of these angular positions having an angular spacing of 90.degree., or another in which the coupled shafts are rotated only through a relatively small angular range and, in this case, measurements are made in a plurality of angular positions having only small angular spacings, and then there is computed therefrom the path which the point of incidence of the light beam would describe in the case of rotation of the shaft through the range of a complete revolution, on the respective light-sensitive detector surface, in order finally to compute the alignment defect from this path.
In conjunction with the implementation of the alignment measurement in accordance with the above known methods, it is frequently necessary or at least desired also to record the angle which a predetermined radial reference direction of the one and/or other shaft includes with the vertical to the earth. For this purpose, separately from the light emitters and position detectors employed in the case of the abovementioned known alignment measurement methods, an inclinometer for establishing the instantaneous angle between the predetermined radial reference direction and the vertical to the earth was hitherto mounted on the respective shaft.
Electrooptical vertical-to-the-earth inclinometers are known which represent the angle information as a rectilinear light-dark boundary on the detector surface of a biaxial electrooptical position detector, which boundary alters its position on the detector surface in corresponding fashion in the course of the rotation of the detector housing about an axis perpendicular to the detector surface, so that the electrical signals generated by the position detector include this angle information.